M o u t h o u m e t A u de A g l y Luzenac St. Barthélémy Castillon Barousse Milhas Trois seigneurs Arize Bessède Salvezines Agly A i g ue t t e Boul za n e Synform Bas Agly Boucheville Synform A X I A L Z O N E A X I A L Z O N E St Gaudens Lannemezan TARBES PAU St Girons Pamiers Foix Tarascon- sur-Ariège Quillan Limoux PERPIGNAN Mauléon- Licharre St Jean Pied-de-Port St Jean-de-Luz SAN SEBASTIAN Oloron-Ste Marie PAMPLONA Lourdes Granulite Peridotite Migmatite Amphibolite Intrusive granitoids Green schiste Silurian Devonian Carboniferous N N 0 5 10 20 30 km A u de A g l y N N A u d e A g l y St. Barthélémy Castillon Barousse Milhas Trois seigneurs Arize Bessède Salvezines Agly A i g ue t t e Boul za n e Synform Bas Agly Boucheville Synform A X I A L Z O N E St Gaudens Lannemezan TARBES PAU St Girons Pamiers Foix Tarascon- sur-Ariège Quillan Limoux PERPIGNAN Mauléon- Licharre St Jean Pied-de-Port St Jean-de-Luz SAN SEBASTIAN Oloron-Ste Marie PAMPLONA Lourdes 0 5 10 20 30 km A X I A L Z O N E 385 560 385 495 495 <450 <450 570 570 580 555 550 550 520 510 <450 405 450 400 <400 560 337 356 387 494 568 353 609 621 353 519 540 560 530 576 572 542 437 532 600 550 610 230 350 200 542 346 300 233 587 333 358 600 289 303 301 320 430 380 594 Cenomanian Santonian sedimentary breccias Peridotite upper Cretaceous to Quaternary Paleozoic basement Triassic to lower Aptian upper Aptian lower Albian middle Albian lower Cenomanian 333 RSCM Peak Temperature this study 570 Temperature from Goldberg and Leyreloup (1990) Simplified geologic map of the North Pyrenean Hercynian Massifs and peridotite outcrops Peak temperatures of the HT/LP cretaceous metamorphism in the Pyrenees Clerc Camille 1, 2 ; Lagabrielle Y. 2 ; Reynaud J.-Y. 3 ; Boulvais P. 4 ; Bousquet R. 4 ; Lahfid A. 1, 5 ; Vauchez A. 2 ; Mahé S. 2, 6 FROM CRUSTAL THINNING TO MANTLE EXHUMATION: WHAT THE PYRENEAN BRECCIA FORMATIONS TELL US ? Corresponding author: [email protected] 1 Laboratoire de Géologie, CNRS-UMR 8538, Ecole Normale Supérieure, Paris, France; 2 Géosciences Montpellier, Montpellier, France; 3 Muséum national d'Histoire naturelle, Paris and ISTeP Paris, France; 4 Géosciences Rennes, France; 5 BRGM / LMA / MIN, Orléans, France; 6 Ecole des Mines, Alès, France A u de A g l y Luzenac St. Barthélémy Castillon Barousse Milhas Trois seigneurs Arize Bessède Salvezines Agly A i g ue t t e Boul za n e Synform Bas Agly Boucheville Synform A X I A L Z O N E A X I A L Z O N E St Gaudens Lannemezan TARBES PAU St Girons Pamiers Foix Tarascon- sur-Ariège Quillan Limoux PERPIGNAN Mauléon- Licharre St Jean Pied-de-Port St Jean-de-Luz BAYONNE SAN SEBASTIAN Orthez Oloron-Ste Marie PAMPLONA Lourdes 0 5 10 20 30 km N INTRODUCTION: Several formations with various breccia types occur in Mesozoic basins disseminated along the North Pyrenean fault, on the northern flank of the French Pyrenees. Due to their location along the Iberia-Europa plate boundary, the North Pyrenean breccia formations represent complex archives documenting the tectonic and L O O K ING FOR A P O S T D OC Cenomanian Santonian sedimentary breccias Peridotite upper Cretaceous to Quaternary Paleozoic basement Triassic to lower Aptian upper Aptian lower Albian middle Albian lower Cenomanian References: Goldberg, J.-M., et A.F. Leyreloup. 1990. High temperature-low pressure Cretaceous metamorphism related to crustal thinning (Eastern North Pyrenean Zone, France). Contributions to Mineralogy and Petrology 104, 194–207; * Barbieri, M., U. Masi, & L. Tolomeo. 1979. Stable isotope evidence for a marine origin of ophicalcites from the north-central Apennines (Italy). Marine Geology 30, 193–204; ** Evans, C.A., & M. Baltuck. 1988. Low-Temperature Alteration of Peridotite, Hole 637A. Proceedings of the Ocean Drilling Program, 103 Scientific Results, 235–239; Milliken, K.L., & J.K. Morgan. 1996. Chemical Evidence for Near-Seafloor Precipitation of Cacite in Serpentinites (Site 897) and Serpentinite Breccias (Site 899), Iberia Abyssal Plain. Proceedings of the Ocean Drilling Program, 149 Scientific Results, 553–558; Skelton, Alasdair D.L., and J. W. Valley. 2000. The relative timing of serpentinisation and mantle exhumation at the ocean-continent transition, Iberia: constraints from oxygen isotopes. Earth and Planetary Science Letters 178, 327–338; *** Weissert, Helmut, & Daniel Bernoulli. 1984. Oxygen isotope composition of calcite in Alpine ophicarbonates: a hydro- thermal or Alpine metamorphic signal ? Eclogae geol. Helv. 77, 29–43; Barrett, Timothy J., & H. Friedrichsen. 1989. Stable isotopic composition of atypical ophiolitic rocks from east Liguria, Italy. Chemical Geology: Isotope Geoscience section 80, 71–84; Demeny, A., T. Vennemann, & F. Koller. 2007. Stable isotope compositions of the Penninic ophiolites of the Köszeg-Rechnitz series. Central European Geology 50, 29–46; Früh-Green, G., H. Weissert, & D. Bernoulli. 1990. A multiple fluid history recorded in Alpine ophiolites. Journal of the Geological Society 147, 959–970. Alpine medium -T ophicalcites* (seawater or metamorphic fluids related) Iberian margin low-Temperature ophicalcites (seawater related)** -8.000 -6.000 -4.000 -2.000 0.000 2.000 4.000 12.00 17.00 22.00 27.00 32.00 δ 13 C δ 18 O veins matrixes clasts W e s t e r n P y r e n e e s M o n c a u p Moncaup E a s t e r n P y r e n e e s Alps*** Iberian Margin** Apennine* Ophicalcites from litterature: This study: Ophicalcites: Agly breccias F o l d Semi-ductile syn-metamorphic breccias: The boudinage of silicic or dolomitic beds is the expression of rheologic heterogeneities during the ductile stretching of the meso- zoic cover. Cataclastic breccias and gouges: The clasts are barely displaced and they display a relatively monogenetic character. These tectonic breccias result from the disruption of the material under cooling conditions. The cata- clastic intervals are mainly hosted by the Triassic and Liassic weaker levels. Anhydrite vein Peridotite Sapphirine bearing sandstone A n h y d r it e v e i n Decoupling along the weaker evapo- ritic levels triggers a juxtaposition of the pre-rift sediments directly on the exhumed mantle. We re-interpret the sapphirine bearing sandstones lying around the eastern Pyrenean perido- tites as remnants of these Triassic evaporites transformed by contact metamorphism with the uprising peri- dotites and lower crustal units. Hydraulic-tectonic breccias: Mid-Cretaceous stretching of the continental crust is accompanied by circulations of hot fluids. These fluids are responsible for allochemical metamorphism, metasomatic reactions and hydrothermalism. Strike-slip Extension N S W E N S W E Transtension Simplified geologic map of the Pyrenees Polymictic sedimentary breccias : Their composition is dominated by clasts of Mesozoic metasediments. Locally, close to subcontinental mantle bodies, the sedimentary breccias include numerous clasts of ultramafic and/or crustal basement rocks. Such breccias are the witnesses of the disruption and c l a s t i c sedimentation of the sedimentary cover in a context of hyper-extended crust and mantle exhumation. Stable isotope composition of some Pyrenean breccias and ophicalcites Syn-metamorphic extensional and/or gravity sliding of pre-rift mesozoic cover on unroofed UB basement - Tearing of Allochtonous carbonates and UB basement exhumation - Chaotic sedimentation inbetween the individualizing rafts and locally over the mesozoic rafts. - Sliding rafts overthrusting breccia 1 - Breccia 2: UB clasts + clasts of mesozoic metasediments + clasts of breccia 1 A B 2 km Mesozoic cover Triassic-Liassic evaporites UB basement Lower crust breccia 1 breccia 1 olistostrom breccia 2 olistostrom breccia 2 Uplift Parallel carbonate veining in mantle Rock - Urdach Hydraulic fracturation in mesozoic marbles - Agly Cataclastic breccias and gouges - Agly Cataclastic breccias of marbles- Aulus trough Cataclastic breccias of peridotite - Aulus trough Polimictic sedimentry breccias - Agly Ophicalcite - Lherz marble-peridotite bearing sedimentary breccias- Lherz The Pyrenean ophicalcites and breccias are displaced toward low d18O values with respect to typical marines ones. This could be the sign of their formation in a continental lacustrine environment. S0 sedimentary evolution of the Pyrenean realm during the Aptian-Albian period. In particular, the North Pyrenean breccia formations have recorded the main stages of crustal thinning, continental break-up and mantle exhumation, which occurred along the North Pyrenean Zone (NPZ).